The present invention relates to motor vehicle drivelines, and in particular, to a method and apparatus for smoothing out oscillations in the vehicle driveline.
Surge in a motor vehicle is caused when the natural frequency of the vehicle""s driveline is activated by a torque transient. The torque transient can be caused by a rapid change in torque from the engine or induced from road disturbances. These torque disturbances cause the vehicle""s driveline to resonate at the natural frequency of the system. The mechanical system is an inertia, spring, inertia configuration with a well documented natural frequency characteristic. The spring component of the system is the contribution of the spring constants of the driveshaft and axles. One inertia in the system is the mass of the vehicle reflected through the tires at one end of the drive system. The other inertia is the engine and transmission components attached to the other end of the system.
The oscillation of the driveline system at the natural frequency will cause an acceleration cycle to be felt in the vehicle. The vehicle will be accelerated on one-half of the cycle and slowed down on the other half of the cycle. This is due to driveline oscillations. Depending on the type of components used in making the vehicle, the frequency range of the natural driveline frequencies range from 1 Hz to 12 Hz.
Accordingly, it is desirable to smooth out the oscillations in the driveline of the vehicle.
A method and apparatus for preventing and/or minimizing driveline surge. A control system monitors engine speed in order to detect perturbations that are higher than the natural frequency of the system. The engine speed is filtered by a high pass filter in order to remove the DC and low frequency components of the engine speed. A counteracting torque is applied to the system to cancel out the torque perturbations that are at or higher that the natural frequency of the system.
The above-described and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims.